1. Field of the Invention
Embodiments of the present invention relate to 1-ethoxy-2-n-alkoxybenzene compounds, and particularly to their use as internal electron donors in catalysts useful for polymerizing olefins. The compounds of the invention provide high activity catalysts.
2. Description of Related Art
Ziegler-Natta catalysts are used to polymerize olefins. These catalysts contain a procatalyst made from an internal electron donor, a titanium source, a magnesium source and a halogenating agent (which may be combined with one of the other components). The use of these catalysts is known where this procatalyst is combined with an external electron donor or more commonly called a selectivity control agent (xe2x80x9cSCAxe2x80x9d) and a cocatalyst. See, e.g., U.S. Pat. No. 5,093,415 to Brady et al.
One class of electron donors taught by the art is veratrole (1,2-dimethoxybenzene) and certain derivatives thereof which incorporate additional substituents on the benzene ring. See, e.g., U.S. Pat. No. 4,971,936 to Wilson et al. See also U.S. Pat. No. 4,107,413 to Giannini et al. However, these specific compounds have certain deficiencies in that catalysts made with them have low catalytic activity ( less than 20 kg polymer/procatalyst per hour) and produce polymers of low crystallinity (e.g., isotactic polypropylene with a xylene soluble content of greater than 30% wt and a L(iso) (1H NMR) of less than 50 even with a SCA). The use of these electron donor compounds solely to produce polymers of low crystallinity is confirmed in Japanese patent application Nos. 2613169 and H1-307519. It is desirable to find electron donors which result in catalysts of improved activity and selectivity.
The novel electron donors (hereinafter xe2x80x9cEDxe2x80x9d) of the present invention are of the formula 
wherein R1 is an ethoxy group, and R2 is an alkoxy group, having from one to ten carbon atoms, and R3-R6 are each individually, hydrogen, a hydrocarbyl group, a hydrocarboxyl group, a silyl group, a nitro group, or a halogen. These EDs are used in the manufacture of olefin polymerization catalysts with procatalysts having magnesium, titanium and halide as essential components.